How to calculate diameter from circumference

Written by allan robinson
  • Share
  • Tweet
  • Share
  • Pin
  • Email
How to calculate diameter from circumference
You can calculate the length of a circle's diameter if you know its circumference. (protractor image by timur1970 from Fotolia.com)

A circumference is the distance around any closed curve; it is also a special type of perimeter. However, it generally refers to the circumference of a circle unless otherwise specified. The term "circumference" also may refer to the length of this distance. A diameter of a circle is a line segment that intersects the centre of a circle with its endpoints on the circle. You can calculate the length of a circle's diameter if you know its circumference.

Skill level:
Easy

Other People Are Reading

Things you need

  • Calculator

Show MoreHide

Instructions

  1. 1

    Learn the significance of pi--a value that is defined as the ratio of a circle's circumference to its diameter. This means that pi = c/d where c is the circumference and d is its diameter. Therefore, the equation d = c/(pi) gives you the diameter of a circle when you know its circumference.

  2. 2

    Know how to express the value of pi for a particular problem. The value of pi rounded to six decimal places is 3.141593, but the exact value of pi can never be known because its expression as a decimal value does not end nor does it repeat. Therefore, any literal value of pi will always be an estimate. You may simply leave it in the solution as "pi" for some problems; for other problems, you may need to provide an approximate value of pi that is accurate to the desired number of decimal places.

  3. 3

    Solve for the diameter when the circumference is a multiple of pi. If the circumference is 4(pi), then d = c/(pi) = 4(pi)/(pi) = 4 using the formula in Step 1.

  4. 4

    Solve for the diameter with an approximation of pi. If the circumference is 12, you know the diameter is d = c/(pi) = 12/(pi). You can estimate the diameter to two decimal places as d = 12/3.142 = 3.82. Note that using a value of pi that is accurate to three decimal places in your calculation ensures two decimal places of accuracy in the final answer. This eliminates the possibility of round-off error in the second decimal place of the final answer.

Don't Miss

Filter:
  • All types
  • Articles
  • Slideshows
  • Videos
Sort:
  • Most relevant
  • Most popular
  • Most recent

No articles available

No slideshows available

No videos available

By using the eHow.co.uk site, you consent to the use of cookies. For more information, please see our Cookie policy.